Already facing social and economic hurdles, millions of poor children with asthma will feel the effects of global warming well before other Americans, according to a report Thursday by the Center for Health and the Global Environment at the Harvard Medical School.

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Asthma among preschool children already is at epidemic levels, the report said, having grown 160 percent between 1980 and 1994 — double the rate for the overall U.S. population. The highest incidence is found among low-income and African-American toddlers.

The report's authors joined the many scientists who believe that rising emissions of carbon dioxide, or CO2, are warming the Earth. CO2 is part of the natural cycle, but mankind over the last century has increased emissions by burning carbon-based fossil fuels.

What comes with warmer Earth
"Rising levels of carbon dioxide, in addition to trapping more heat, promote pollen production in plants, increase fungal growth and alter species composition in plant communities by favoring opportunistic weeds (like ragweed and poison ivy)," the report stated.

Interactive: The greenhouse effect
On top of that, "other emissions from burning fossil fuels in cars, trucks and buses form photochemical smog that causes and exacerbates asthma, while diesel particulates help deliver and present pollen and mold allergens to the immune system in the lungs."

Christine Rogers, a co-author and researcher at the Harvard School of Public Health, called the report "a real wake-up call for people who mistakenly think global warming is only going to be a problem way off in the future or that it has no impact on their lives in any meaningful way."

'One-two punch'In a statement accompanying the report, she said poor and minority children in urban areas "get hit with a powerful one-two punch: exposure to the worst air quality problems and the additional allergen exposure arising from global warming. In addition, global warming is causing pollen seasons to arrive earlier in the spring."

The report was endorsed by the American Public Health Association and prepared for the Civil Society Institute, a liberal nonprofit that aims to create working solutions to social conflicts.

Paul Epstein, another co-author and associate director at the Center for Health and the Global Environment, urged policymakers to do more to reduce carbon dioxide emissions. The Bush administration is relying on incentives to industry to reduce emissions, while the European Union is spearheading efforts for mandatory cuts.